1. Field of the Invention
The present invention relates to a valid medium management system for managing the validity of a storage medium such as a magneto-optical disk, etc. storing a script, a certified copy, or a duplicate of a document.
2. Description of the Prior Art
A number of documents are prepared and stored on storage media such as magneto-optical disks, etc. these days. Papers stored in storage media also cover various fields. For example, they are a development plan and design prepared by a designing division and a sales division of a company, papers relating to family register and others about the residents prepared by a city office, a ward office, etc., papers transmitted and received between companies and organizations, etc.
The security of these documents is very important. For example, it is necessary to store papers such that they cannot be falsified, and the script of a document and a certified copy of the document can be clearly distinguished from each other when they are stored on a storage medium. Especially, when a script, a certified copy, etc. are to be correctly stored, an authority is required to certify a script, a certified copy, etc. To act as an authority, the authority needs a qualification stamp, for example, an electronic key, assigned only to the authority. That is, it is necessary to recognize a target document as a script, recognize a target document as a certified copy, and put an electronic signature to each document using a signature key of the recognizer. Furthermore, to prevent a copy or falsification by a third party, an important document can also be requested to be stored in a medium area in which no copy can be made.
However, in the conventional technology, for example, if a generator of a script unconsciously writes the script to a plurality of storage media, then a plurality of copies of the script, which is to be unique, are made. In addition, if a duplicate document is stored on a storage medium for exclusively storing a script, or if a script document is stored on a storage medium for exclusively storing a duplicate, then there occurs a mix-up, and consistent altering and adding processes cannot be performed on the script document.
On the other hand, there has been a system recently suggested for managing a storage medium by adding a unique number to the medium. That is, with an increasing number of multimedia of these days, a unique number is assigned to each storage medium to correctly protect the copyright of a storage medium. The related information is stored in a non-writable area for a common user.